Thanks to these changes, the sound absorption inside the chamber has increased rapidly, says researcher Leandro de Santana from the Engineering Fluid Dynamics group, led by Kees Venner who runs the special testing facility. ‘All noises above 160 Hz get absorbed by the triangle-shaped wedges on the walls, meaning they absorb practically all the noise produced by the air flow, which can reach up to 240 km/h. Noise measurements are currently the main objective of this lab, but we also test aerodynamic properties of various objects.’
Sound isolation
De Santana explains the necessity of proper sound isolation inside the anechoic chamber, the test section of the aeroacoustic wind tunnel is also known as the ‘silent’ wind tunnel. ‘The things we are testing are getting more and more silent. That means that the sound protection we previously had wasn’t working properly anymore. We therefore decided to update the acoustic lining of the anechoic chamber. We replaced the metallic plates with custom-made wedges made of mineral wool. The previous acoustic lining was 15 cm thick, the current one is 60 cm thick.’
‘We conduct noise measurements for large aircraft companies, wind turbines or ventilation systems, for example’, De Santana continues. ‘When you measure noise, you want to detect only the noise produced by the tested object, nothing else.’
